Character representing glow discharge tube and system for selective excitation of the character representing electrodes thereof



April 5, 1966 R. A. MILLIKEN CHARACTER REPRESENTING GLOW DISCHARGE TUBEAND SYSTEM FOR SELECTIVE EXCITATION OF THE CHARACTER REPRESENTINGELECTRODES THEREOF 3 Sheets-Sheet 1 Filed Sept. 14 1962 FII-j l FIB-EAPHl 5, 1966 R. A. MILLIKEN 3,244,923

CHARACTER REPRESENTING GLOW DISCHARGE TUBE AND SYSTEM FOR SELECTIVEEXCITATION OF THE CHARACTER REPRESENTING ELECTRODES THEREOF -Filed sept.14, 1962 s sheets-sheet a Aprll 5, 1966 R. A. M|| 1KEN 3,244,923

CHARACTER REPRESENTING GLOW DISCHARGE TUBE AND SYSTEM FOR SELECTIVEEXCITATION OF THE CHARACTER REPRESENTING ELECTRODES THEREOF Filed Sept.14, 1952 5 Sheets-Sheet 5 l l l|| llllll United States Patent MCHARACTER REPRESENTENG GLOW Dl'SCHARGE TUBE AND SYSTEM FDR SELECTIVEEXCHA- TION F THE CHARACTER REPRESENTING ELEC'ERDES THEREGF Rankin A.Miilihen, Hayward, Calif., assignor, by mesne assignments, to Friden,Inn, San Leandro, Calif., a corporation of Delaware Filed Sept. 14,1962, Ser. No. 223,673 12 Ciairns. (Cl. Mii-109.5)

This invention relates to gaseous indicator glow tubes.

More particularly, this invention relates to indicator glow tubes of thetype particularly suited for use with circuits which utilize bin-aryprinciples of operation. Tubes of this type may be designated asdecoder-indicator tubes because they are capable, by reason of theirelectrode arrangement, of not only indicating numbers stored inelectronic counters, but of also functioning to interpret, or decode,the pattern of electrical signals appearing upon the output terminals ofan electronic counter of the type in which said pattern of signalsdoesnot bear a simple one-to-one relationship to the exciting terminals ofsaid indicating glow cathodes, or at least contributing substantially tothis decoding function by way of reduction of apparatus external to thetube necessary for performance of this function.

Tube arrangements of this type may be seen in United States Patent No.2,906,906, upon which the present invention is an improvement.

Up to the present time, decoder-indica-tor tubes of this type have notproved completely satisfactory because of the complexity of theirelectrode configurations, and the consequent need for basing-arrangements involving considerable numbers of contact pins.

Accordingly, one object of the instant invention is to provide animproved cathode indicator glow tube having combined anode-shieldelectrodes which perform several functions hitherto performed byseparate electrodes.,

Another object of the instant invention is to provide an improvedcathode indicator glow tube particularly suited for use in conjunctionwith binary-type counting circuits, and for providing a direct visiblereadout therefrom.

Yet another object of the instant invention is to provide an improveddecoder-indicator glow tube which may be mounted in an envelope of thestandard 7pin miniature type, having a standard 7-pin basingarrangement, without sacrifice of any of the functional capabilities orsputter protection features of prior devices, though it is to beunderstood tha-t the invention is by no means limited to such a basingarrangement.

A still further object of the present invention is to provide astructural 4arrangement of mutually cooperating cathodes, insulators,and exciting electrodes Iwhich obviates the necessity of threading many`cathodes and insulators onto side rods, thereby making possibleminiaturized assemblies of a compactness hitherto attainable only atvery great cost.

Briefly, the principles and objects of the instan-t invention may beembodied in a tube which comprises a gasiilled envelope containing aplurality of indicator cathodes shaped 'm the form of desired, e.g.,numerical, indicia, and capable of manifesting their presence bysustaining a cathode glow ithereabout. If, for example, this tube is tobe used in a decade counter, it may contain indicator cathodes in theform of the numerals 0' through 9. These indicator electrodes may bearranged in groups (e.g., all of the odd-number indicator cathodesconstituting one group, and all of the even-number indicator cathodesconstituting another group). According to the invention a combinedanode-shield electrode will be associated with the rst group, andanother electrically 3,244,923 Patented Apr. 5, 1966 ICC independentcombined anode-shield electrode will be associated with the secondgroup. The association between a combined anode-shield electrode and itscorresponding group consists in part in the combined anode-shieldelectrode at least partially embracing, or surrounding, the associatedgroup of indicator cathodes. The extent to which the combinedanode-shield electrode embraces, or surrounds, its associated group ofindicator cathodes will be determined principally by two factors: (1)the necessary electrical isolation of its associated group of indicatorcathodes from the effects of any combined anodeshield electrodeassociated with any other group of indicator cathodes, and (2) thedesired degree of protection of the wal-ls of the envelope, and otherstructure within the envelope, from sublimation, or sputtering ofindicator cathode material thereupon. Thus, is will be seen that thecombined anode-shield electrodes, or anodeexcitation shield electrodes,serve two shielding functions, Viz., the function of shielding theassociated group of indicator cathodes from excitation by otherelectrodes outside the associated combined anode-shield electrode, andthe function of protecting portions of the tube outside the associatedcombined anode-shield electrode from sublimation, or sputteringj ofindicator cathode material thereupon. In addition, the combinedanode-shield electrode serves the third function of providing anexciting field for provoking cathode glow upon any desired one, or more,of its associated indicator cathodes. This is in contrast to prior artdevices wherein the sputter shielding, spurious excitation shielding,kand exciting functions were served by distinct and different electrodesfor the same group of indicator cathodes. It will be apparent to thoseskilled in the art, then, that so combining these three functions in asingle combined anode-shield electrode for each group of indicatorcathodes makes possible the provision of a -tube having all thecapabilities and advantages of prior art devices, yet at Ithe same timebeing characterized by a reduced number of the electrodes, and a reducednumber of necessary base pins.

In addition to these three electrical functions o-f the combinedanode-shield electrodes of the invention, the cornbined anode-shieldelectrode may, in a preferred embodiment, also function mechanically tosupport the indicator cathodes in desired relation within the tube byclampingly engaging a stack comprising said cathodes and supportinginsulating means therefor. That is, the combined anode-shield electrodesmay not only embrace, or surround their associated groups of cathodesfor the above detailed purposes of electrical function, but may alsoclampingly engage the associated groups of cathodes for the purpose ofmechanical support. It is to be understood, however, that the electricaladvantages arising from the provision of my combined anode-shieldelectrode may be embodied in a more conventional tube structure (c g.,having side rods, or support posts, to mount the indicator cathodes asshown in United State Patent No. 3,042,826) without departing from thescope of my invention.

lt will further be apparent to those skilled in the art that the numberof contact pins, or base pins, necessary may be reduced to a minimum byproviding a contact pin for each of the combined anode-shield electrodesand a contact pin for each pair of indicator cathodes which may beselected one from one group and one from the other group. By thisarrangement the number of necessary base pins is reduced to seven in atube capable of providing decoding in a binary coded decimal countersystem. Other combinations of indicator cathode electrodes and combinedanode-shield electrodes may be made as required by a particular code orcircuit application. ln addition, several sets, each consisting of twoor more groups of indicator cathodes, a combined anode-shield electrodebeing associated with each group, may be provided so that a simultaneousreadout of a plurality of characters may be .achieved from within asingle envelope,

In operation of a decoder-indicator tube of the type of the instantinvention, a single indicator cathode in a group may be caused to glowby the application of the proper exciting voltage between the selectedindicator cathode and the combined anode-shield electrode associatedwith this indicator cathode, Thecombined anodeshield electrodesassociated with the other groups of indicator electrodes within thecommon envelope will pre lilv parent portion opposite cover mesh 18 (asshown in FIG. 1) through which all of 4the indicator Vcathodes in theenvelope may be viewed, combined anode-shield electrode 7 being equippedwith front and rear cover meshes 18 and combined anode-shield electrode6 being equipped with a cover'rnesh 18 for this purpose, all as shown inFIG. 3. A sealed-off exhaust tubulation 11 is provided in the stem pressof envelope 1. Further, the combined anode-shield electr-odes 6 and 7may beheld in insulated, spaced relation by means of insulatorassemblies 8, as shown in FIG. l, which insulator assemblies, may, forinstance,

p comprise an insulated metal rod having a tubular invent interactionbetween the combined anode-shield electrode of the group including theIselected indicator cathode and the indicator cathodes of the othergroups, thereby preventing spurious, or undesired, glow of an indicatorcathode in a group other than the group including the selected indicatorcathode. Y l

The invention is described in greater detail by reference to theaccompanying drawings wherein:

FIG. a shows a spacing insulator frame according to the instantinvention; Y

FIG. 5b shows a positioning insulator frame according to the instantinvention;

FIG. 6 shows an alternative embodiment of the instant invention whereinthe walls enclosing the groups of cathodes are defined in part byportions of insulating spacer means; and K FIG. 7 is a schematicrepresentation of a modified indicator tube embodying the instantinvention and adapted to provide multiple numeral readout.

Referring to the drawings, and more particularly to FIG. 1, one form ofindicator tube according to the instant invention comprises an envelope1 which has been' evacuated of air filled with anionizable gas, such asneon, argon, or the like, at a suitable pressure, for example, in; therange offabout 40 toy 120 mm. of mercury, and, if desired, one of theheavier gasesy or vapors, such as mercury. The envelope includes a baseportion, or Vstem press, through which conductive base pins, or contactpins, extend, and by means of which electrical connection may be made toexternal electrical circuit means.

The tops of some, or all, of the contact pins 2 may be substantiallycoplanar, thus being adapted to support tube mount assembly 3 by meansof the lower mica end spacer 4, the mount assembly being constrainedvagainst the tops of the base pins 2 by means, for instance, of clipssuch as shown at 17, which may be tweezer-welded to the top of one orseveral base pins, or' by means of frictional engagement of lingers 5 onthe mica end spacers 4 withthe interior of the wall of envelope 1, orboth. It will be apparent to those skilled in the art that it may oenecessary to shield the inner portions of base pins 2 associated withindicator cathodes 9, and the indicator cathode leads 10, from theanode-shield electrode base pins andrleadsV and such portions of thecombined anode-shield electrodes 6 and 7 as project below lower end mica4. This may be done, for example, by coating Ythe inner portions of basepins `2 and cathode leads 10 with glass frit, or Alundum, by oxidizingthe inner ends of the base pins and the leads 10, by locating the leads10 suflciently close tothe combined anode-shield electrodes ,ias torequire a higherp'otential to strike a glow therebetween than anypotentials employed in the usual operation of the tube, or any`combination of these expedients found desirable by the Ytube designer.The envelope 1 also includes av transsulator disposed thereupon andlocated between ears provided on the combined anode-shield electrodes asshown of the large apertures in end mica 4', thesev inwardlydependingears being of just suticient width to provide the desired spacing.

TheV electrode elements of a tube according to the invention may be seento include the following by comparison of FIGS. l and 3: a first, orback, combined anode-shield electrode 6 made of conductive material,which'may be toraminou's to only a sufficient degree to expose itscontained indicator cathodes to View through the viewing portion of theenvelope, or may be comprised to a larger degree, or entirely, offoraminous material. ri `his combined anode-shield electrode mayconsist, in greater or lesser part, of insulating material. A second, orfront, anode-shield electrode, like the back anode-shield electrode,'may be wholly or partly foraniinous, and may consist wholly ofconductive material, or may be partly of insulating material. A group ofassociated indicator cathodes is contained in each of said anode-shieldelectrodes, said anode-shield electrodes serving to excite theassociated group of indicator cathodes, rto shield the associated groupof indicator cathodes` against the elfects` of other electrodes, and toshield the portionsl of the tube located therewithout from sublimationor-sputtering of the material of the'y associated indicator cathodes.

Each of the combined anode-shield electrodes may be directly, weldedlyor otherwise, connected to the inner end of one of the base pins 2,which connections may serve to maintain the-mount structure 3 inposition longitudinally of envelope 1, either in insulatedv contact withthe ends of the remaining base pins 2, or spaced therefrom.

`The indicator cathodes 9 of the tube may take substantially any desiredshape, for example, they may be in the shape of characters such asnumbers, letters, arbitrary symbols, c g., plus or minus signs, or thelike. In one form ofthe tube, as shown in FIG. 4, the indicator cathodesmay be provided in the form of numbers, the totall of such indicatorcathodes being ten in number, includingthe numbers 0 through 9. Theindicator cathodesA may be'v fabricated from any suitable metal, forexample, stainless steel, aluminum, Nichrome, molybdenum, orV the like;and they may be made in any suitable fashion, for example, by etching,stamping, formying from wire, or the like.

A.The indicator cathodesy 9 are mounted in an aligned stack, as shown inexploded view in FIG. 3, such that their planes are substantiallyparallel, and are suitably shaped and of such size that the separateelements thereof are, displaced laterally with respect to each other sothat none Vis obstructed by the others, and each is substantiallycompletely visible through the wall of envelope, 1 opposite the outercover mesh 18. 1n addition, eachv of the indicator cathodes withinenvelope 1 Yis provided, by means of indicatorv cathode leads 10,

withv connection to one of the base pins 2 other than afa/tasas thoseused for supplying potential to the combined anodeshield electrodes, oneindicator cathode from within the front combined anode-shield electrode,and one indicator cathode from within the back combined anodeshieldelectrode being connected in common to one of 5 the base pins 2. Thearrangement of theseelectrical connections of the 'combined anode-shieldelectrodes 6 and 7 and the indicator cathodes 9 with the base pins 2 isshown in FIG. 2.

FIG. 3 shows the several parts of a tube of the instant invention inexploded view. As may be seen from this ligure, the mount structure 3according to the instant invention is assembled by stacking a desiredplurality of the indicator cathodes 9, the indicator cathodes beingspaced apart by means of insulating spacing frames 13 and. held indesired relation to the apertures in spacing frames 13 by means ofinsulating positioning frames 14. As will be apparent to those skilledin the art from consideration of-FIG. 3 the stack made up of theindicator cathodes associated with a given combined anodeshieldelectrode and the insulating spacing and positioning frames'associatedtherewith is assembled and inserted into the associated anode-shieldelectrode which rst is closed at one end, and after the insertion ofthis stack the cover mesh at the other end of the anode-shield electrodeis fastened in place (e.g., by means of spot welding) thereby clampinglymaintaining the associated indicator cathodes in desired spaced relationwithin the combined anode-shield electrode. As shown in FIG. 3, anopening 31 is provided in the bottom wall of each anode-shield electrodewhereby the leads 10 of the indicator cathodes may pass through thecombined anodeshield electrode without electrically contacting it. Leads1t) are preferably fabricated separately from the lower ears 12 ofindicator cathodes 9, and then welded or otherwise affixed thereto .atthe proper angle to pass out through channel 16 of insulating frames 14(FIG. 5b), clearing the edge of slot 31 of the associated anode-shieldelectrode structure by an amount determined to prevent spurious glowthereat. The insulating spacing frames 13 and the insulating positioningframes 14 may be fabricated from many types of insulating material wellknown to those skilled in the art. Alternatively, due to the design ofthese frames, according to instant invention, these frames may bepunched, stamped, etched, or otherwise formed from oxidizable metallicmaterials, and then treated, e.g., by dipping in an oxidizing solution,and subjected to heating in an oven, thereby producing an insulatingstructure adapted for use as an insulator in carrying out the instantinvention, which insulating structure has the advantage of being formedby the simpler processes available for producing metallic parts, ascompared with the processes available for producing thin insulatingparts. For instance, these insulating frames 13and 14 may be producedfrom sheet nickel which is vfirst electroformed, stamped, or punched,and then aluminized and oxidized, such a method being generallysuggested in UnitedStates Patent No. 2,891,184. Having assembled theback mount structure (comprising the back combined anode-shieldelectrode and 'its associated indicator cathodes and insulating frames)into an integral unit, and having similarly assembled the front mountstructure, the two may then be assembled into a single, unitary mountstructure 3 by passing insulated metal rods through insulators 8 andthrough holes in the upper and lower ears of the combined anode-shieldelectrode structures, and placing additional insulating washers on saidinsulating rods at the opposite side of said ears from insulators 8, ifdesired, and then distorting the ends of said insulated rods bycompressio-n, thereby locking the front and rear mount structuresinsulatedly together in the manner well known in the art (see, forexample, the support post structure shown and described in connectionwith FIG. 2 of United States Patent No. 3,042,826).

After performing the above steps, the complete mount structure 3 may beadaped for positioning within tube envelope 1 by passing end micas 4over the ends of mount structure 3 as far as ears 24 provided on thelonger sides thereof, passing ears 24 through slots 22 in the end micas,and bending the outer portion of the ears 24 along the outer surfaces ofend micas 4. The completed mount assembly 3 and end micas 4 may then beassembled upon the base pins 2 in the stem press by welding the lowerears of the combined anode-shield structures to a pair of base pins 2,by means of clips 17, or both. The cathode leads 1t) may then beconnected to appropriate base pins 2, as by tweezer welding the stem andenvelope sealed, and the envelope evacuated through tubulation 11, whichis then sealed olf.

When assembled as described above, the indicator cathodes 9 will benonmutually-interferingly registered as shown in FIG. 4, wherein a partof the cathodes making up the full set, O through 9, has been eliminatedfor clarity of illustration.

The contour of one of the insulating spacing frames 13 is shown in FIG.5a. It will be noted from this iigure that the upper and lower edges ofthe frame aperture are provided with inwardly projecting portions whichserve to maintain indicator cathodes 9 in spaced relation by separatingtheir ears 12, and also serve to present only the numeral-definingportions of cathodes 9 to view through cover mesh 18.

The insulating positioning frames 14 are illustrated in FIG. 5b. It willbe noted from this ligure that the insulating positioning frames 14 areprovided with inward projections of substantially the same contour asthe inward projections in insulating spacing frames 13, but providedwith ear receivers 1S in which the ears 12 of the associated indicatorcathode will be emplaced during assembly. Further, the insulatingpositioning frames 14 are provided with lead channels 16 communicatingfrom one of the ear receivers 15 through the lower portion of the frame14. As may be seen from FIG. 3, the indicator cathode leads 10 will passthrough the channels 16, and will be constrained by the limited lateralextent of lead channel 16 from contacting the edges of slot 31 in thecombined anode-shield electrodes 6 and 7. It will be apparent to thoseskilled in the art that by the provision of this particular lead channelstructure and cooperating orientation of indicator cathode leads 1@ withrespect to the indicator cathodes, a controlled spacial relation betweenthe indicator cathode leads 1% and the edges of slot 31 may bemaintained, thereby taking advantage of the lower limb of the Paschenslaw curve for mutual insulation purposes and assuring maximum isolationbetween the leads or adjacent cathodes.

FIG. 6 indicates an alternative construction which may be employed infabricating a device according to the invention. In this alternativeembodiment the cornbined anode-shield electrodes 6 and 7 do not passthrough a central aperture in the end micas, as shown, for instance, inconnection with FIG. 3, but rather the bottom and top walls of thecombined anode-shield electrodes are provided by the end micas (one endmica 25 being shown in the drawing). The electrically conductive partsof the combined anode-shield electrodes then comprise at wall memberswhich are held in mutual xed, insulated relationship by means of ears 23comprising a part thereof and being passed through slots in the endmicas and then twisted to produce a permanent deformation and consequentinterlocking relationship with the end micas. In this construction covermeshes 18 are provided as before, as are the groups of associatedindicator cathodes (which groups are not illustrated in FIG. 6 forrea-sons of clarity).

The principles of the instant invention may also be embodied in a tubewhich includes more than two sets of groups of electrodes. Such a tubeis shown schematically in FIG. 7 wherein four groups of indicatorcathodes are generally indicated, respectively, as 27, 28,V 29 and 30,the two groups 2.7 and 2S constituting one coacting set of electrodes,and the two groups 29 and 30 constituting a second coacting set. It willbe apparent from FIG. 7 to those skilled in the art that the set ofgroups 27 and 28 is capable of displaying any numeral from through 9,while the set made up of groups 29 and 3@ is capable of independentlydisplaying any numeral from 0 through 9. A typical binary coded decimalcounter system in which the tube of the instant invention may beemployed is .shown in Unitedy States Patent No. 2,906,906. f u

Since numerous changes may be made in the abovedescribed apparatus, anddiferent embodiments of the invention may be made without departing fromthe spirit thereof, it is intended that all the matter contained inl theforegoing description and shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An indicator tube comprising: a irst group of character-shapedindicator cathodes adapted to glow, a second group of character-shapedindicator cathodes adapted to glow, and a combined anode-excitationshield electrode associated with each yof said groups VVof cathodes,each of said combined anode-excitation shield' electrodes at leastpartially surrounding its associated groupV of cathodes, whereby each ofsaid combined anodeexcitation shield electrodes isY adapted to excite atleast one of its associated cathodes to glow and is also adapted toshield its associated group of cathodes from glowing when any of thecathodes of the group associated with lthe other anode-excitation shieldelectrode is excited to.

glow. Y

2. An indicator tube comprising: a rst group of character-shapedindicator cathodes adapted to glow, a second group of character-shapedindicator cathodes adapted to glow, and an enclosure including acombined anode-excitation shield yelectrode associated with each of saidgroupsk of cathodes, each of. said enclosures at least partiallyenclosing its associated group of cathodes and being adapted to exciteat least one of itsassociated group of cathodes to glow and to preventits associated groupv of cathodes from glowing when any cathode of theother of said groups of associated cathodes is excited to glowl by itsassociated combined anodeexcitation shield electrode, the walls definingsaid enclosures being comprised at least in part of insulating material.Y

3. An indicator tube comprising: a first group ofcharacter-shapedrindicatcr cathodes adapted to glow, a second group ofcharacter-shaped indicator cathodes adapted to glow, and an enclosureincluding as part of'its definingV walls a combined anode-excitationshield electrode associated with each of said groups of cathodes, eachof said enclosures at least partially surrounding its associated groupof cathodes.

It. An indicator tube comprising: a first group of character-shapedYindicator cathodes adapted' to glow, a second group of character-shapedindicator cathodes adapted to glow, and an enclosure including Vaspar-tv of its dening Walls a combined anode-excitation shield electrodeassociated with each of said groups of cathodes, each of said enclosuresat least partially surrounding its associated group of cathodes andhaving insulating materialk as a part of its defining walls. y

5. An indicator tube comprising: a plurality of sets of groups ofcharacter-shaped indicator cathodes adapted to glow and an enclosureincluding a combined anode-I excitation shield electrode associated witheach'of said groupsof cathodes, each of said enclosures at leastpartially surrounding, its associated group of cathodes and beingadapted to excite at least one of its associated group of cathodes toglow and to4 prevent its associated group of cathodes from glowing whenany cathode of any of the other groups of its set is excited to glow byits associatedy combined"anode-excitation shield electrode, the wallsdeiining said. enclosures being comprised at leas't in part ofinsulatingmaterial.

6. An indicator tube comprising: a first charactershapedv indicatorcathode adapted to glow, a second character-shaped indicator cathodeadapted to glow, a combined anode-excitation shield electrode associatedwith each of saidl cathodes, yand an envelope having no more than sevencontact pins for makingl electrical contact between said cathod'es andcombined. anode-excitation shieldV electrodes and apparatus locatedexternally thereof passing therethrough. f

7. An indicator tube comprising: a iirst group of character-shapedindicator cathodes adapted to glow, a second group of character-shapedindicator cathodes adapted to glow, a combined anode-excitation shieldelectrode associated with each of saidgroups of cathodes, each of saidcombined anode-excitation shield electrodes being adapted to excite atleast one of its associated group of cathodes to glow andv to preventitsassociated group of cathodes from glowing'when any cathode of the otherof said groups of cathodes is excited to glow by its associated combinedanode-excitation shield electrode, and an. enveiope enclosing saidcathodes and combined .anode-excitation shield electrodes and having:disposed.Y there through n contact pin-s, where n'=C-|2, and. C equalsthe number'of cathodes in one of said groups.

' 8. An indicator tube comprising: a plurality of sets of groups ofcharacter-shaped indicator cathodes adapted' to glow, a combinedyanode-excitation shield electrode associated with each of said groups ofcathodes, each of said combined anode-excitation shield electrodes beingadapted' to excite rat least one of its associated group of cathodes toglow and to prevent its associated group of cathodes from glowing whenany cathode of. any of thel other groups of its set is excitedy to` glowby its associated combined anode-excitation shieldy electrode, and anenvelope enclosing said cathodesV and combined anode-excitation shield'electrodesr and having disposedv therethrough n contact pins, where andC equals the number of cathodes in one of said groups, S equals thenumber of said sets, and G equals the numberrof said groups.

9.. An indicator tube, comprising: a first charactershaped indicatorcathode adapted tov glow, a second character-shaped indicator cathodeadapted to glow, and an enclosuredefined'in part byka combinedanode-excitation shield electrode associated withv each of saidcathodes, each of said combined anode-excitation shield electrodes beingadapted to excite'its associated cathode to glow and to prevent itsassociated cathode from glowing when the other of saidv cathodes. isexcited to glow by its associated combined anode-excitation shieldelectrode, each of said enclosures at least partially surrounding one ofsaid groupsV and being further detined by insulating members which alsoserve in part assupporting means for said combined anode-excitationshield electrodes.

10. An indicator tube comprising: a first group of fiveVcharacter-shaped indicator cathodes adapted' to glow, a second group ofve character-shaped indicator cathodes adapted to glow, and a combinedanode-excitation shield electrode'associated with each of said cathodes,each of said combined' anode-excitation shield electrodes being adaptedto excite its associated cathode to glow and to prevent its associatedcathode from glowing when the other of said cathodes is excitedto glowby its associated combined anode-excitation shield electrode, andcoacting with au insulating spacer member to define an enclosureA atleast partially enclosing each of said groups of cathodes.

11. An electrode assembly for use in a glow indicator tube comprising: aplurality of character shaped indicator cathodes, a rst plurality ofinsulating frames surrounding each of said indicator cathodes, a secondplurality of insulating frames insulatedly spacing said rst plurality ofinsulating frames, and a combined anode-excitation shield electrodeclampingly engaging said frames and cathodes and maintaining said framesand `cathodes in fixed relation without the use of other relationmaintaining means.

12. An electrode assembly for use in a glow indicator tube comprising: aplurality of character-shaped indicator cathodes, a first plurality ofinsulating frames surrounding each of said indicator cathodes, a secondplu rality of insulating frames insulatedly spacing said first pluralityof insulating frames, and a combined anodeexcitation shield electrodeclampingly engaging said frames and cathodes, said frames and cathodesbeing free of ycontinuous members passing therethrough.

References Cited bythe Examiner JOHN W. HUCKERT, Primary Examiner.

I AMES D. KALLAM, Examiner,

L. ZALMAN, Assistant Examiner.

1. AN INDICATOR TUBE COMPRISING: A FIRST GROUP OF CHARACTER-SHAPEDINDICATOR CATHODES ADAPTED TO GLOW, A SECOND GROUP OF CHARACTER-SHAPEDINDICATOR CATHODES ADAPTED TO GLOW, AND A COMBINED ANODE-EXCITATIONSHIELD ELECTRODE ASSOCIATED WITH EACH OF SAID GROUPS OF CATHODES, EACHOF SAID COMBINED ANODE-EXCITATION SHIELD ELECTRODES AT LEAST PARTIALLYSURROUNDING ITS ASSOCIATED GROUP OF CATHODES, WHEREBY EACH OF SAIDCOMBINED ANODEEXCITATION SHIELD ELECTRODES IS ADAPTED TO EXCITE AT LEAST